term:

Landmark

landmark n

often attrib
1 : an object (as a stone or tree) that marks a boundary of land
2 : an event or development that marks a turning point or stage [a decision]
3 : a structure (as a building) of unusual historical or aesthetic interest
;esp
: one that is officially designated and set aside for preservation

Source: Merriam-Webster's Dictionary of Law ©1996. Merriam-Webster, Incorporated. Published under license with Merriam-Webster, Incorporated.